Strength Training, Studies
May 29, 2016
Training frequency is one of the most hotly debated topics in the field of resistance training. While traditionally the term frequency has been associated with how many days a week you work out, a potentially more important variable is the number of times a given muscle group is trained per week.
The internet is littered with varying opinions as to optimal training frequency for maximizing muscle hypertrophy. Some preach the typical bodybuilding “bro-split” which involves training each muscle group once a week with high volumes per session, whereas others propose training each muscle as many as 6 days a week with lower per-session volumes is the best way to get jacked. Problem is, all these opinions are largely anecdotal with limited scientific support. Seems hard to believe, but there hasn’t been a whole lot of research on the topic, and the studies that have been carried out have employed a variety of methodological designs that makes it difficult to sort out a conclusion at face value.
In an attempt to achieve better clarity on the effects of frequency on muscle growth, I recently collaborated on a meta-analysis with colleagues James Krieger and Dan Ogborn. In case you’re not aware, a meta-analysis pools data from all studies on a given subject to provide greater statistical power and thus enhance the ability to draw practical inferences.
Here’s the lowdown:
What We Did
A literature search was conducted to locate all studies that directly compared measures of hypertrophy for different weekly lifting frequencies using traditional resistance training programs. Only human studies with healthy subjects were considered, and study duration had to last a minimum of four weeks.
A total of 10 studies were identified that met inclusion criteria. 7 of the studies, comprising a total of 200 subjects, investigated muscle group frequency while the other 3 studies assessed training session frequency when the number of weekly times working a muscle group was matched.
What We Found
We first looked at the effects of frequency as a binary predictor. Simply stated, this means that the higher frequency condition in a study was compared to the lower frequency condition, irrespective of how many days a week the muscle group was trained. Thus, a 2 day-a-week vs 1 day-a-week was treated the same as a 3 day-a-week vs 1 day-a-week. In this model, there was a clear benefit for higher frequency training of a muscle group. The effect size – a measure of the meaningfulness of results – was 48% greater for the higher frequency conditions (0.49 vs 0.30, respectively), translating into an average hypertrophy increase of 6.8% versus 3.7% for higher vs lower frequencies, respectively. Moreover, as shown in the accompanying chart, every study on the topic showed a benefit to training with higher frequencies.
Due to an insufficient number of studies looking at training 1, 2, or 3 days per week, we were unable to produce reliable estimates on the hypertrophic effects of specific lifting frequencies. Similarly, with only 3 studies looking at training session frequency when groups were matched for frequency of training per muscle group, data was insufficient to produce reliable estimates for effects on hypertrophy.
What are the Practical Implications
The primary take-away from the meta-analysis is that there appears to be a pretty clear benefit to training muscle groups with higher weekly frequencies. At the very least, the study shows that training a minimum of 2 days a week is needed to maximize muscle growth. Unfortunately there simply aren’t enough studies to make more concrete determinations as to the precise number of times that a muscle should be trained each week for optimal growth. Nevertheless, training a muscle just once a week was shown to promote substantial muscle growth. So the claims made by some that the typical bro-split only works for juiced-up bodybuilders are patently false.
It’s important to realize that research studies are relatively short-term, usually lasting 6 to 12 weeks. Problem is, you can’t necessarily extrapolate that results found would continue over time. This is particularly true of a variable such as frequency, as high training frequencies may ultimately lead to an overtrained state and thus have a negative impact on muscle development. Given such a possibility, it may be prudent to periodize training frequency, varying the number of times a muscle is trained each week in a systematic fashion. It also indicates a potential benefit to instituting regular deload periods, where a week of reduced frequency, volume, and/or intensity is strategically integrated into your program every month or so to facilitate recuperation and regeneration.
Importantly, remember that research reports the average responses, but there are generally large inter-individual differences in results. Some may respond best to higher frequencies while others might do better with lower frequencies. Use research to guide your programming, then experiment to see what works best for you.
Sorry, the comment form is closed at this time.
Entries (RSS)
Great job Bradley! Thank you for writing this up.
Comment by Bret Contreras — May 29, 2016 @ 11:25 pm
Great article. I’d be really interested to know how training frequency differs per muscle group. From observing myself, I notice that the muscles on the arms and legs prefer higher frequency while muscles on the torso prefer less frequency but higher volume.
Comment by Dan Salcumbe — May 30, 2016 @ 1:59 am
Good article. As a 73 year old gent being in a multi exercise phase since 1953 I have trained dozens of different ways. Just about any article on fitness / muscle growth can be used as a ” does this apply to me ” ponder. I have done 4-5 workouts per day to 1 in a week. Seems like I stay fit with many workouts per week. The word workout should be renamed funout , there is no work to it. Working a joint / muscle to fatigue at 70 plus is stupid to me. I do 8 reps with a weight I could do 12. No sweating, grunting, grimace, breathing hard.
Comment by Ken — May 30, 2016 @ 5:43 am
Cheers Bret!
Comment by Brad — May 30, 2016 @ 7:21 am
Good article!
However, I missed whether the two groups were corrected for total weekly training volume. If not, the positive effects of high training frequency could also be explained by the difference in volume between groups, and not solely by the higher frequency.
Comment by Sander — May 30, 2016 @ 11:02 am
Interesting piece. Questions it raises for me:
What is the correlation between hypertrophy gains and strength gains? The phenotypes of power lifters appears different to me than body builders, suggesting size and strength may not be linearly related. My guess is that operationally defining “strength gain” is harder in these studies, so it is easier to measure size… But is that the construct of greatest interest (it may well could be, but I’m personally more interested in strength and health)?
Is there consistency in these studies between using “noobs” or “longer-term lifters”? If so, which group was studied in these studies? If not, I’m guessing that adds considerable variability to the data set, and, in fact, may be a moderating / interacting variable hiding some interesting findings.
Kudos for trying to use *data* to address some of the issues that have traditionally been ruled by bro-science. It is an uphill battle, mostly because there are so many variables in play that all interact with each other (e.g., age, gender, body fat, lean mass, years lifting, sets, reps, diet, etc., etc., etc.). Add that there is inadequate funding for high-quality studies to be performed, and the data are a mess. It is telling (and sad/shocking) that it is 2016 and you could only find ten (10!) studies that fit the inclusion criteria. Isn’t this one of the most basic questions in the fitness industry?
Keep up the great work, and thanks for sharing.
Comment by Big Chief — May 30, 2016 @ 11:16 am
Sander:
Five of the seven studies equated volume. It’s doubtful that the other 2 studies that did not equate would have significantly impacted results, IMO.
Comment by Brad — May 30, 2016 @ 1:09 pm
[…] Schoenfield writes about this hotly debated topic and shares the findings of his research in THIS blog post. Methinks you will enjoy the […]
Pingback by Random Thoughts | Bret Contreras — May 30, 2016 @ 9:36 pm
“…optimal training results can be achieved from exercising the whole body twice/week (and, for some muscle groups and some individuals, once/week) is supported by the research literature. Several studies have found no differences between results gained from training once, twice or three times/week (61,62,76,80), one study found training either twice or three times/week to be better than training once/week (78), one study found training twice/week better than training three times/week (77), and another study found training three times/week better than training five times/week (79). The only study that has found high-frequency (i.e. greater than three times/week) training to be more effective is Marx et al. (47), a study loaded with confounding variables. Therefore, it seems reasonable to conclude that for most individuals, training each muscle at the most twice/week (and, in many instances not more than once/week) will provide optimal results. ”
47. Marx JO, Ratamees NA, Nindl BC, Gotshalk LA, Volek JS, Dohi, K et al. Low volume circuit versus high volume periodised resistance training in women. Med Sci Sports Exerc2001;33:635-643.
61. Graves JE, Pollock ML, Foster D, Leggett SH, Carpenter DM, Vuoso R, Jones A. Effect of training frequency and specificity on isometric lumbar extension strength. SPINE1990;15:504-509.
62. Carpenter DM, Graves JE, Pollock ML, Leggett SH, Foster D, Holmes B, Fulton MN. Effect of 12 and 20 weeks of resistance training on lumbar extension torque production. Phys Therapy 1991;71:580-588.
76. Taafe DR, Duret C, Wheeler S, Marcus R. Once weekly resistance exercise improves muscle strength and neuromuscular performance in older adults. J Am Geriatric Soc1999;47:1208-1214.
77. Carroll TJ, Abernethy PJ, Logan PA, Barber M, Mc
Eniery MT. Resistance training frequency: strength and myosin heavy chain responses to two and three bouts per week. Eur J App Phys 1998;78:270-275.
78. DeMichele PL, Pollock ML, Graves JE, Foster DN, Carpenter, D, Garzarella L et al. Isometric torso rotation strength: effect of training frequency on its development. Arch Phys Med Rehabil1997;78:64-69.
79. Rozier CK, Schafer DS. Isokinetic strength training: comparison of daily and three times weekly patterns. Inter J Rehabil Res 1981;4:345-351.
80. McLester JR, Bishop P, Guilliams ME. Comparison of 1 day and 3 days per week of equal-volume resistance training in experienced subjects. J Strength Conditioning Res 2000;14:273-281.
https://fhww.files.wordpress.com/2008/03/smith.pdf
thoughts?
Comment by Marko Sabo — June 2, 2016 @ 11:28 am
Marko:
First, that review is over 10 years old and thus doesn’t include recent studies. Second, simply looking at “statistical significance” is misguided as it doesn’t take statistical power into account of the relevant research. Our study was a meta-analysis that pooled all data from relevant studies and the evidence was rather compelling that at least 2 days a week per muscle group is needed to maximize gains over the long haul.
Comment by Brad — June 2, 2016 @ 3:38 pm
In my experience; I have intuitively trained muscles I enjoyed training (such as biceps/triceps) more often, about every 4-6 days. I have noticed most measurable growth and response in these higher frequently trained muscle groups. After years of training once a week to twice a week (4 day cycle), now I am forcing myself to train all muscle groups at this higher frequency and I see anecdotal benefits.
Comment by Daniel J Dorazio Jr — June 5, 2016 @ 12:57 pm
Hey Brad,
If I go from training same body part 1 x per week to 2 x per week (every 72 hrs), should I train same intensity (heavy for 8 reps) both times per week? Or is it better to go heavy once and then the second time in the week go light but do supersets or something?
Thanks (great article btw).
Comment by James — June 28, 2016 @ 9:51 am
What was the total volume of the week ?? This is the main factor, because you have to achieve a minimun volumen of volumen per week. Therefore, could be intersting to compare the same volumen of work with different frequencys.
Comment by Alejandro — August 15, 2016 @ 5:01 pm
Great points on the study being short-term, reporting average responses and the need to periodize training frequency. Love how you outlined these limitations.
Cheers!
Etiennw
Comment by Etienne Juneau — November 5, 2016 @ 5:01 pm